Following along.
I have this issue on my right quarter on my ‘71 vert. When it was flange repaired with a graft from a ‘72 quarter around 1990-2 it happened.
No reproduction panels back then.
I’ve been debating what to do as well. The flange seam is visible inside the trunk.
I found a picture of a '73 on my computer. I had downloaded it from Bring a Trailer website (not sure when) of an alleged 3800 mile '73 Cuda. Sure enough, its on the left side like yours.
Beautiful car!
I noticed on the tail panel that the Cuda emblem was left of the license plate. Is that a '73 thing? My '72 has it right of the license plate.
The hood not sitting down in the corner is a result of improper adjustment of the hood so I have read.
https://www.forebodiesonly.com/forum/threads/r-t-hood-wont-sit-down-at-rear.32555/
https://www.forebodiesonly.com/forum/threads/fender-hood-alignment.13713/